The present invention relates, in a magnetic tape cartridge where a single reel with magnetic tape wound thereon is rotatably housed within a cartridge case, to the reel of the magnetic tape cartridge.
In magnetic tape cartridges, which are being used as storage media that are employed in external storage units for computers, etc., there is known a type where a single reel with magnetic tape wound thereon is rotatably housed within a cartridge case. This magnetic tape is employed to archive data for computers, etc. Since important information has been stored, the magnetic cartridge is constructed so that problems, such as tape jamming, etc., do not occur and that the magnetic tape is not pulled out of the cartridge case unexpectedly when not being used, such as when being archived, etc.
The reel is provided with a reel gear which meshes with the driving gear of the rotation means of a cartridge drive mechanism so that it is rotatable and also provided with a magnetic metal plate for keeping the meshed state therebetween.
Hence, when rigidly attaching the aforementioned metal plate to the reel, it is preferable to hold this metal plate to the inside surface of a metal mold and provide the metal plate and the reel integrally by insert molding, because they can be easily manufactured. However, in the insert molding which injects molten resin from a gate provided in the center of the central hole of the annular metal plate, the resin injected under high pressure flows directly to the inner peripheral surface of the central hole of the metal plate. Because of this, there is a possibility that the resin will enter the space between the metal plate and the inside surface of the metal mold and therefore the metal plate cannot be held at a predetermined position in the reel. There is another possibility that in a molded reel product where resin has flowed to the top surface side of the metal plate because of the above-mentioned entrance of resin, it cannot be assured that the metal plate is parallel with the magnet of the rotation means of the cartridge drive mechanism and therefore chucking failure will occur.
If the injecting pressure is reduced to prevent the above-mentioned entrance of resin, a portion insufficiently filled with resin will occur and thus the dimensional precision of the molded produce will be reduced.
The present invention has been made in view of the problems mentioned above. Accordingly, it is a first object of the present invention to provide a reel of a magnetic tape cartridge which can be manufactured by insert molding, without reducing pressure under which resin is injected and without causing resin to enter the space between the metal plate and the inside surface of the metal mold.
The above-mentioned reel, incidentally, is constructed of a cylindrical hub with tape wound on the outer peripheral surface thereof, and flanges extending in disc form from both ends of the hub so that the wound tape is interposed therebetween. Generally, in the case of constituting the reel with resin molded components, one of the two flanges and the hub are molded integrally and the other flange molded as a separate body is rigidly attached to the end portion of the hub.
The rigid attachment between the hub and the flange is usually performed by an ultrasonic welding method using weld bosses or an energy director. The ultrasonic welding shortens manufacturing time, and is low in running cost because a portion melted from a molded component is used as a binder, so ultrasonic welding is now being widely used for manufacturing reels.
Thus, in the rigid attachment of the reel by ultrasonic welding, it is difficult to assure satisfactory attachment precision with enhancements in recording density and recording precision. That is, if data is recorded with high density, the lateral deflection of tape will have an influence on recording and reproducing characteristics. For this reason, the traveling height precision of tape is required to be very strict. In the ultrasonic welding of the hub and the flange which are resin-molded components, however, it is extremely difficult to rigidly attach the flange to the hub at a right angle to the rotation axis of the hub with high precision. Because of this, the development of a high-precision reel has been hastened so that it can satisfactorily meet the high-density recording being required in recent years. In addition, as the recording capacity of the magnetic tape is increased, as described above, the tension of winding a magnetic tape that is wound on the reel becomes greater. Because of this, it is necessary to make the strength of attachment between the hub and the flange stronger.
The aforementioned problems with the ultrasonic welding will be described in detail. Rigid attachment type reels are shown in FIG. 10 and FIGS. 11 and 12. The example of FIG. 10 is a type in which the longitudinal end portions of magnetic tape are respectively fixed to two reels housed in the cartridge case and the magnetic tape is wound from one of the reels onto the other. In the reel, a hub 153 formed integrally with one flange 154, and another flange 155 formed as a separate body, are connected together by ultrasonic welding. Within the cylindrical hub 153 with an outer peripheral surface on which magnetic tape is wound, six weld bosses 156 protruding in a direction parallel to the rotation axis of the hub 153 are provided at regular intervals in the circumferential direction. On the other hand, at positions corresponding to the weld bosses 156, a disc flange 155 has transmission holes 157 into which the weld bosses 156 are inserted. The flange 155 is placed on the hub 153 so that the upper ends of the weld bosses 156 inserted into the transmission holes 157 project from the flange 155. Then, with the annular tip end surface of a welding horn pressed against the upper end portions of the weld bosses 156, ultrasonic waves are applied to the upper portions of the weld bosses 156 to melt the weld bosses 156. The melted weld bosses 156 are flattened so that the flange 155 is rigidly attached to the hub 153.
Similarly, in the reel shown in FIGS. 11 and 12, a hub 153 formed integrally with one flange 154, and another flange 155 formed as a separate body, are connected together by ultrasonic welding. Within a cylindrical hub 153, three weld bosses 158 are provided at regular intervals in the circumferential direction. A disc flange 155 has transmission holes 159 into which the weld bosses 158 are inserted. As with the aforementioned, the flange 155 is placed on the hub 153 so that the weld bosses 158 are inserted into the transmission holes 159. Then, the upper end portions of the weld bosses 158 are melted and flattened with the 3-point annular tip end surface of a welding horn so that the flange 155 is rigidly attached. Note that the above-mentioned weld bosses 156 and 158 may be welded by heating.
In the rigid attaching by the weld bosses 156 and 158, however, pushing force will remain exerted on the central portion of the attached flange 155 and deform the flange 155, if the welding by the welding horn is too strong. If the welding is too weak, the flange 155 will not be satisfactorily attached due to underwelding of the weld bosses 156 and 158 and chatter of the flange 155 against the hub 153 will occur. Furthermore, if a plurality of weld bosses 156 and 158 are unequally welded, a warp will develop in the flange 155. If such a reel rotates, deflection of the flange 155 will occur and accordingly deflection of the magnetic tape will occur. Thus, it is difficult to manage welding conditions suitably.
FIGS. 13 and 14 show a rigid attachment type reel having an energy director. A flat fixing portion 160 in the form of a ring is formed in an end surface near the outer peripheral surface of a cylindrical hub 153 on which magnetic tape is wound. At the inner peripheral surface of a disc flange 155, a generally triangular cross-section energy director is formed to protrude in ring form from the flange surface. The flange 155 is placed on the hub 153, and with the flange 155 on the energy director 161 pressed against the annular tip end surface of a welding horn, ultrasonic waves are applied so that the energy director 161 is melted and rigidly attached to the hub 153.
In the rigid attaching by the energy director 161, however, it is difficult to weld the energy director 161 uniformly over the entire circumference. If the degree that the energy director 161 is melted varies over the circumference, the flange 155 will tilt and therefore deflection will occur during rotation. Also, since the energy director 161 is melted by concentrating ultrasonic energy on the energy director 161 without contacting the welding horn directly with the energy director 161, the design of the energy director 161 for melting into a suitable state and the setting of ultrasonic welding conditions are complicated and difficult.
In addition, there are resins that cannot be welded by the aforementioned ultrasonic welding, so the number of usual resins is limited. Furthermore, the ultrasonic welding has the following disadvantages: the wall thickness of the hub is increased to assure weld surfaces; wall thickness becomes unequal between the flange and the hub which are integrally formed; flatness of the flange portion is reduced; and cylindricity of the hub is reduced.
The present invention has been made in view of the points described above. Accordingly, it is a second object of the present invention to provide a reel that is capable of enhancing rigid attachment precision between the hub and the flange even whey they are resin molded components, and reducing tape deflection.
To achieve the above-mentioned first object of the present invention, there is provided a single reel of a magnetic tape cartridge in which the reel with magnetic tape wound thereon is rotatably housed in a cartridge case,
a magnetic metal plate being molded integrally on a reel bottom surface by insert molding;
the metal plate being formed into an annular shape having a central hole; and
in a reel bottom wall closing the central hole of the metal plate with resin injected from a gate at the center of the central hole of the metal plate when the insert molding is performed, a recess being formed between a gate trace at the center portion of the bottom wall and an inner peripheral surface of the central hole of the metal plate.
It is preferable that the recess be formed into the shape of a circumferential groove by an annular protruding portion provided in a metal mold.
According to the reel of the present invention achieving the first object of the present invention, when the magnetic metal plate with a central hole is molded integrally on the bottom surface of the reel by insert molding, a recess is formed in the reel bottom wall closing the central hole of the metal plate with resin, between a gate trace at the center portion of the bottom wall and an inner peripheral surface of the central hole of the metal plate. For this reason, a protruding portion is formed in the metal mold so that it corresponds to the recess. The resin, injected from the gate during insert molding, is regulated so as to flow in a relatively thin space for molding the reel bottom wall, by the protruding portion of the metal mold. As a result, the resin flows to the inside surface of the metal plate without colliding directly with the inner peripheral surface of the metal plate, and the metal plate is pushed against the metal mold surface. Therefore, the reel of the present invention has the following advantages: the entrance of resin into the space between the metal plate and the inside surface of the metal mold can be prevented; the metal plate is not moved; the injection pressure can be set higher; the molding precision of the reel can be assured; and desired insert molding can be performed.
In accordance with the second object of the present invention, there is provided a reel of a magnetic tape cartridge in which a disc flange is rigidly attached to an end portion of a cylindrical hub having an outer peripheral surface on which tape is wound,
the hub end portion and the flange being rigidly attached by an adhesive.
It is preferable that the adhesive be a light hardening type adhesive and further preferable that it be an ultraviolet ray hardening type adhesive or visible light hardening type adhesive.
It is desirable that the hub and the flange be rigidly attached at a position away from the outer peripheral surface of the hub by the adhesive. In that case, it is preferable that the hub and the flange be rigidly attached at a surface approximately parallel to the axis of rotation of the hub by the adhesive. The surface may be inclined at an angle of 1 to 10 degrees. Furthermore, the hub and the flange may be rigidly attached at a surface perpendicular to the rotation axis of the hub. For instance, a collar portion which contacts with the inner peripheral surface of the hub is provided in the flange, and the inner peripheral surface of the hub and the outer peripheral surface of the collar portion are rigidly attached by an adhesive.
The end surface of the hub may be provided with a stepped portion. In this case, it is preferable that the hub and the flange be rigidly attached by the adhesive at a portion of the hub which is radially inward from the stepped portion.
It is preferable that at least either an adhesion surface of the hub or an adhesion surface of the flange be roughened and rigidly attached by an adhesive.
The aforementioned adhesive is applied to a predetermined place on the adhesion surface of the hub or flange in a predetermined amount by a dispenser, etc. The flange is assembled on the hub, while being positioned with respect to the hub. Then, they are rigidly attached by hardening the adhesive.
According to the reel of the magnetic tape cartridge of the present invention achieving the second object of the present invention, the disc flange is rigidly attached to the end portion of the cylindrical hub having an outer peripheral surface on which tape is wound, by the adhesive. As a result, the reel of the present invention has the following advantages: dimensional precision can be satisfactorily obtained by rigidly attaching the flange at a right angle to the axis of rotation and to the degree that deformation does not occur; the lateral deflection of tape can be reduced; and it can satisfactorily meet enhancements in recording density and recording precision, even if the hub and the flange are resin-molded components.
If a light hardening type adhesive, particularly an ultraviolet ray hardening type adhesive, is used as the aforementioned adhesive, a reduction in the hardening time makes mass production and step simplification possible.
In the reel, in which the hub and the flange are rigidly attached by an adhesive at a position away from the outer peripheral surface of the hub, for example, at a surface approximately parallel with the axis of rotation of the hub, or at a portion of the hub which is radially inward from the stepped portion, the aforementioned adhesive can be prevented from overflowing to the outer peripheral surface of the hub on which tape is wound.
If at least either an adhesion surface of the hub or an adhesion surface of the flange is roughened and rigidly attached by an adhesive, this reel can enhance adhesive strength and allow an increase in winding tension.
In addition, the use of resin enables a combination of a resin hub and a resin flange, having no weldability, which cannot be welded by ultrasonic welding. In the ultrasonic welding, the flatness of the hub due to unevenness in wall thickness between the hub and the flange which are integrally formed, and cylindricity of the flange portion, are reduced because of assurance of adhesion surfaces. However, in the present invention, molding is possible with equal wall thickness; molding precision of the hub is enhanced; and a reel of a magnetic tape cartridge with higher precision is obtainable.